In information transfer using light (optical communication), the technique disclosed in Unexamined Japanese Patent Application Kokai Publication No. 2016-38809 is known. In detail, this technique is intended to acquire information corresponding to change in light emitted by a light source in a transmission device and included in images captured by a reception device in an optical communication system. In such an optical communication system, the non-emission period of the light source is used as the synchronization timing in some cases.